We carry out direct numerical simulations of two-dimensional turbulence with forcing at different wavenumbers and resolutions up to 327682 grid points. In the absence of large-scale drag, a state is ...reached where enstrophy is quasi-stationary while energy is growing. In the enstrophy cascade range the energy spectrum has the form E(k) = εω2/3k−3, without any logarithmic correction, where εω is the enstrophy dissipation and is of the order of unity. However, is varying between different simulations and is thus not a perfect constant. This variation can be understood as a consequence of large-scale dissipation intermittency, following the argument by Landau (Landau & Lifshitz, Fluid Mechanics, 1959, Pergamon). In the presence of a large-scale drag, we obtain a slightly steeper spectrum. When forcing is applied at a scale which is somewhat smaller than the computational domain, no vortices are formed, and the statistics remain close to Gaussian in the enstrophy cascade range. When forcing is applied at a smaller scale, long-lived coherent vortices form at larger scales than the forcing scale, and intermittency measures become very large at all scales, including the scales of the enstrophy cascade. We conclude that the enstrophy cascade with a k−3-spectrum is a robust feature of the two-dimensional Navier–Stokes equations. However, there is a complete lack of universality of higher-order statistics of vorticity increments in the enstrophy cascade range.
ABSTRACT
Complex systems in research and development exhibit important characteristics that might present significant systems engineering challenges due to lack of clear customers, system goals, ...previous development experience, etc. Such systems are characterized through the existence of multiple proposed preliminary architectures, no implemented prototypes, and no agreed upon standards and protocols. We refer to these systems as Research‐Intensive Complex Systems (RICS). RICS requirements are not well‐defined, and RICS are exposed to a wide variety of risks and uncertainties. The main source of the RICS domain knowledge, requirements, and goals are research publications and reports. There is often a lack of clear goals, and many goals are ambiguous or conflicting. This paper evaluates the effectiveness of the Knowledge Acquisition in autOmated Specification (KAOS) method applied to smart metering system, as an example of a sustainability‐related RICS. The evaluation is performed using a set of qualitative criteria with respect to KAOS's ability to elicit and specify goals for RICS in comparison to the implemented goal models.
High-resolution simulations of forced two-dimensional turbulence reveal that the inverse cascade range is sensitive to an infrared Reynolds number, Reα = kf/kα, where kf is the forcing wavenumber and ...kα is a frictional wavenumber based on linear friction. In the limit of high Reα, the classic k−5/3 scaling is lost and we obtain steeper energy spectra. The sensitivity is traced to the formation of vortices in the inverse energy cascade range. Thus, it is hypothesized that the dual limit Reα → ∞ and Reν = kd/kf → ∞, where kd is the small-scale dissipation wavenumber, will lead to a steeper energy spectrum than k−5/3 in the inverse energy cascade range. It is also found that the inverse energy cascade is maintained by non-local triad interactions.
An ethnographic description of a typical match day of Ritual del Kaos barra fans provides elements to discuss the consumption of alcohol as a specific practice of aguante. For the young ...Mexican-organized supporters of professional football clubs the concept of aguante has become the key concept for their daily practices. America Football Club fans of Ritual del Kaos display aguante practices under different denominations. Three of them are descontrol, colorido and carnaval. These concepts are in some sense contradictory one to the other but at the same they are complementary. Descontrol is practiced as if was completely “irrational” and purely emotional. Colorido and carnaval are apparently pure organized and rationalized practices. Nevertheless, the three of them are a combination of emotional and rationalized actions. In that sense, the interpretation of this phenomenon will be given by the melodramatic imagination coordinates.
En la ingeniería de software se utilizan diferentes tipos de diagramas para lograr la calidad que debe cumplir el sistema para desarrollar. El diagrama de objetivos de KAOS (Knowledge Acquisition in ...aut Omated Specification) es utilizado en las primeras fases del ciclo de vida de software (definición y análisis) para expresar a los interesados la importancia del sistema futuro. Sin embargo, en los trabajos que utilizan este diagrama no se logra identificar una automatización entre el lenguaje natural y los elementos básicos (objetivos, entidades, operaciones y agentes) que conforman dicho diagrama. En este artículo se propone la construcción de una ontología y la definición de un conjunto de reglas morfosintácticas y semánticas para: (i) caracterizar los elementos básicos a partir del uso del lenguaje natural en idioma español, (ii) minimizar la ambigüedad semántica presente en el universo del discurso, (iii) obtener automáticamente los elementos básicos, y (iv) elaborar automáticamente dicho diagrama.
En este artículo, se propone un modelo para obtener de manera automática los elementos básicos del diagrama de objetivos de KAOS (objetivo, agente y entidad) y minimizar la ambigüedad semántica de ...tipo polisémica en la obtención de dichos elementos. Además, se valida el modelo propuesto mediante casos de estudio. El diagrama de objetivos de KAOS (Especificación Automática de Adquisición de Conocimientos; del inglés Knowledge Acquisition Automated Specification) suele ser utilizado en la fase de definición y análisis de la ingeniería de software para determinar los procesos que se efectúan en la organización que solicita el software. En los diferentes trabajos publicados en la literatura científica que usan el diagrama de objetivos de KAOS subsisten algunos problemas causados por la elaboración manual del diagrama por parte del analista (confusiones, subjetividad, ambigüedad, entre otros). Con la metodología propuesta los elementos básicos del diagrama de objetivos de KAOS se obtienen de manera automática evitando errores como los mencionados.
A very simple model for train stopping is used as a vehicle for investigating how the development of a control system, initially designed in the continuous domain and subsequently discretized, can be ...captured within a formal development process compatible with standard model based refinement methodologies. Starting with a formalized requirements analysis using KAOS, an abstract model of the continuous system is created in the ASM formalism. This requires extensions of the KAOS and ASM formalisms, capable of dealing with quantities evolving continuously over real time, which are developed. After considering how the continuous system, described as a continuous control system in the state space framework, can be discretized, a discrete control system is created in the state space framework. This is re-expressed in the ASM formalism. The rigorous results on the relationship between continuous and discrete control system models that are needed to establish provable properties of the discretization, then become the ingredients of a retrenchment between continuous and discrete ASM models, and are thus fully integrated into the formal development. The discrete ASM model can then be further refined towards implementation.
Self-adaptation is imposing as a key characteristic of many modern software systems to tackle their complexity and cope with the many environments in which they can operate. Self-adaptation is a ...requirement per-se, but it also impacts the other (conventional) requirements of the system; all these new and old requirements must be elicited and represented in a coherent and homogenous way. This paper presents FLAGS, an innovative goal model that generalizes the KAOS model, adds adaptive goals to embed adaptation countermeasures, and fosters self-adaptation by considering requirements as live, runtime entities. FLAGS also distinguishes between crisp goals, whose satisfaction is boolean, and fuzzy goals, whose satisfaction is represented through fuzzy constraints. Adaptation countermeasures are triggered by violated goals and the goal model is modified accordingly to maintain a coherent view of the system and enforce adaptation directives on the running system. The main elements of the approach are demonstrated through an example application.
Managing OAM&P Requirement Conflicts Chentouf, Zohair
Journal of King Saud University. Computer and information sciences,
09/2014, Letnik:
26, Številka:
3
Journal Article
PDF
